This invention relates to radiologic measuring devices, and more particularly, to the use of radiation in measuring bone structure.
The diagnostic use of radiation in evaluating bone structure has recently been applied in assessing bone demineralization that occurs with advancing age. Bone mineral is lost from all parts of the skeleton, and at a linear rate from the lumbar spine, starting at about 35 years of age. The resultant demineralization results in a high risk of fractures with an increased associated mortality and morbidity. In evaluation of the spine, there is a very good correlation between dual photon densitometry measurements of bone density and fracture resistance in excised vertabrae subjected to compression testing. It is also important to evaluate mineral loss in the hip, as appendicular losses often match or exceed spine loss in patients over 70.
Dual photon absorptiometry enables non-invasive quantitative analysis of bone mineral in regions of the body that were previously inaccessable using single photon absorptiometry. The use of two photon energies minimizes errors that result from irregular body contour and soft tissue inhomogeneities. Essentially, two photon energies are necessary to allow discrimination of two substances of a given system. In this case between bone mineral and soft tissue. The most commonly used photon energies in dual photon scanning are 44 and 100 KeV. The measurements of the attenuation of this radiation as it passes through the body yields the bone mineral density.